I'd like to start off with the Knights Base because i found it the most easiest to defend. So X represents spots you SHOULD NOT place the chests, why?. Because those spots make it easier for the enemy to snatch it and run off easily and without even attacking off they go!. The Circles are spots i found very very useful if you got a team defending because it takes the enemy longer to run up and snatch the chests + if you got some defenders then it'll be even better to stop their attack. I prefer to stack up the chests in either 1 of those circle corners, so for example i'd choose the left corner and stack up the 6 chests in the corner so all i need to do is focus my attention and defend that 1 corner, very simple and easy :)

Here we got the Vikings. I'm not to much of a Viking player but the spots i have marked in the picture are very useful to me. Placing the chests in the middle of the boat makes it harder for both Pirates and Knights to steal, the good thing is neither side has a bigger chance of stealing than the other. An example would you be if you placed the chests on say the left of the boat, the pirates have more of an advantage because it's placed on their side as their base is to the left making it easier for them to run,grab and escape down the secret hole, as for the Knights if all 6 chests are placed on the left it will take them longer to run and grab + if you're defending correctly they will be an easy target due to how long it'll take to grab a chest on the left side of the boat and escape into the right building. So my point is if you place the chests in the middle of the boat, the pirates and knights have a balance chance of stealing the chests, 1 does not get a bigger advantage over the other.

For the Pirates it's easier well in my opinion to defend if you got some good Sharpshooters on your side because of the massive open space advantage they got when it comes to defending. So spots for the pirates would be the back here you see in the picture i placed a chest at the very back, the 2 Xs are spots players alwayssss place the chests at and it's very easy for Vikings/Knights to just run up,grab it, *Uses chest special* and off they go! when the chest is at the back it's easier to keep on eye on since sharpshooters should be behind while maybe Captains/Skirmishers are in front, just depends on how you wanna defend but i chose throwing it at the back to be better due to how easy it is to defend as pirates and it'll take the Vikings/Knights longer to run up to, since as soon as they are at the back chest they already got the Pirates team just beating them up.

I hope this guide helps you out, and atleast changes your mind on where to place the Chests! since the X spots is where players always alwaysss! place the chests so the Circle Spots are the spots i always place the Chests at since i find it's better and more useful + harder for the enemy team to snatch but it all depends on how you defend your base!